Ion pump and assembly method

Abstract

An ion pump and method for assembling the same are described. The ion pump includes a pump housing enclosing a pump chamber, one or more anodes, a set of cathode plates, and mounting means for supporting the cathode plates. The mounting means is configured to support the cathode plates in a predetermined position within the pump chamber. The mounting means includes support means defining a linear path, the linear path having an open end, and the cathode plate is slidable into position along the linear path through the open end.

Description

[Technical Field]

[0001] The field of the invention relates to ion pumps and methods for their assembly. [Background technology]

[0002] An ion pump is a trap-type vacuum pump that can include an array of cylindrical anode tubes arranged between cathode plates, with the opening of each anode tube facing one of the cathode plates. A potential is applied between the anode and cathode, while a magnet on the opposite side of the cathode plate generates a magnetic field aligned with the axis of the anode cylinder. The ion pump operates by trapping electrons within the cylindrical anode through the combination of the potential and magnetic field. As gas molecules move toward one of the cylindrical anodes, the trapped electrons collide with the molecules, ionizing them. As a result, positively charged ions are accelerated toward one of the cathode plates by the potential between the anode and cathode, and the bare electron(s) remaining at the cylindrical anode are used to further ionize other gas molecules. The positively charged ions are captured by the cathode and thus removed from the vacuum space. Summary of the Invention [Problem to be solved by the invention]

[0003] There is a desire to miniaturize some ion pumps, which makes them more difficult to assemble. [Means for solving the problem]

[0004] In one aspect, an ion pump is provided that includes a pump housing enclosing a pump chamber, at least one anode, at least one cathode comprising a plate, and at least one mounting means configured to support the at least one cathode at a predetermined position within the pump chamber, the at least one mounting means including support means defining a linear path, the linear path having an open end, such that the cathode can slide along the linear path through the open end and into the predetermined position.

[0005] In ion pumps, precise alignment of the cathode and anode is important for the pump to function efficiently, and therefore they must be securely fastened in place. Accessing the interior of the pump housing to fasten the cathode in place can be difficult, especially in small ion pumps. Furthermore, the cathodes in ion pumps are typically formed from a different material than the pump housing, making them difficult to weld to the pump housing. The inventors have recognized this problem and addressed it with an attachment means for the cathode plate(s) that defines a path that allows the cathode to be placed in place and then slid and held securely in place without the need for welding or attempting to access and manipulate the holding means.

[0006] In some embodiments, the ion pump includes a pair of the mounting means for each of the at least one cathode plate, the pair of mounting means configured to support opposite ends of each of the at least one cathode plate, each of the pair of mounting means comprising support means defining the linear path having the open end.

[0007] The cathode plate can be supported from one side, but in some embodiments it will be supported from both sides, which ensures it is held securely in place. The two sides are parallel to each other, and the two paths defined by the respective support means extend parallel and linearly so that the cathode can be slid into position longitudinally.

[0008] In some embodiments, the at least one attachment means includes a rail and the pathway comprises a groove extending along the length of the rail.

[0009] In another embodiment, each of said at least one attachment means comprises a plurality of support means arranged in an array, said array defining said path.

[0010] In yet another embodiment, the at least one attachment means comprises a groove on an inner surface of the pump housing.

[0011] The mounting means can have many forms, so long as it provides an open end and a linear path for the cathode plate to slide into position. The mounting means can be a groove in the housing, which has the advantage of not requiring additional mounting means and can be formed by removing material from the interior surface or by forming a raised surface during manufacture. Alternatively, the mounting means can be one or more rails mounted within the pump housing, or can be formed from a plurality of separate elements, possibly protrusions with recesses or protrusions offset from one another on their left and right sides along the line of the path, so that the cathode can slide into position along the path and be held by its left and right sides.

[0012] In some embodiments, the attachment means can be welded to the inner surface of the pump housing. In this regard, the cathode plate is typically formed of a different material than the pump housing, and therefore, welding the cathode plate in place is not possible. The attachment means can be made of the same material as the pump housing, possibly stainless steel, and can itself be welded. Alternatively, the attachment means can be held in place by a retaining means, such as a bolt. For very small pumps, access to the retaining means may be difficult, and welding may be a desirable solution. The attachment means can be fixed in place before assembling the pump.

[0013] In some exemplary embodiments, the pump comprises two cathode plates attached to opposite ends of the at least one anode.

[0014] In some embodiments, the at least one anode comprises a cylinder and the at least one cathode is mounted perpendicular to a longitudinal axis of the cylinder.

[0015] In some embodiments, the ion pump comprises a plurality of cylindrical anodes mounted in an array, the axes of the cylindrical anodes being parallel to one another.

[0016] In some embodiments, at least one of the at least one cathode plate includes at least one post extending from a surface of the at least one cathode plate toward the at least one anode and configured to protrude into the corresponding at least one cylindrical anode.

[0017] In some cases, the cathode may have support posts extending from it. These support posts are additional electron sources and may improve the performance of the pump. These support posts extend into the cylindrical anode and may make the pump more difficult to assemble. One advantage of allowing the cathode to be slid into place is that the anode can be mounted so that the cylinder surrounds one end of the support post, and the anode plate(s) and cathode plate(s) can then be slid into place together, and then secured in place, possibly by welding a portion of the anode(s) to the wall of the pump facing the opening.

[0018] In some embodiments, the ion pump comprises a miniature ion pump having a nominal pumping speed of less than 4 liters / second.

[0019] Embodiments are particularly useful for small ion pumps, such as those with nominal pumping speeds of less than 4 liters per second, and in some cases less than 3 liters per second. The pump housing can be configured with dimensions less than 5 cm. In this regard, the pump housing can be linear, with each dimension being less than 5 cm. If the pump is linear, the opening through which the cathode plate(s) slide can be an open sidewall of the pump housing, and a cover can then be welded over the opening. In other embodiments, the pump can be tubular, the opening can be an opening in the tubular wall, and the cover can be welded over the opening when the cathode(s) and anode(s) are in place. In some embodiments, the cover can be a sidewall or portion of the tubular wall, and in other embodiments, for example, the cover can comprise an inlet to the pump, optionally surrounded by a flange for attachment to a vacuum chamber.

[0020] In a further aspect, a method of assembling an ion pump according to one aspect is provided, the method comprising: sliding the at least one cathode plate into an opening in a wall of the pump housing along the path defined by the support means; and fixing the at least one anode to a power supply point in the wall of the pump housing facing the opening.

[0021] In some embodiments, the method further includes obscuring at least a portion of the opening by welding one of a closure plate or an inlet flange to the pump housing around the opening.

[0022] In some embodiments, the pump housing is straight and the closure plate comprises a sidewall of the housing.

[0023] One particular advantage of pumps according to embodiments is that they are easy to assemble, in that the cathode plate can be slid along a path defined by the support means of the mounting means. The anode can be fixed to the power supply point, and then the opening through which the cathode slides can be welded closed, or an inlet flange can be welded over the opening.

[0024] In some embodiments, the method includes sliding two cathode plates within the pump housing along a path defined by support means on left and right sides of the at least one anode.

[0025] In some embodiments, the method includes an initial step of positioning the at least one cylindrical anode such that support posts extending from the at least one cathode plate extend into the at least one cylindrical anode, and the step of sliding the at least one cathode plate into position includes sliding the at least one anode and the at least one cathode plate into position together.

[0026] If the cathode plate has posts that extend into the cylindrical anode, then the cathode and anode can be slid together through the open side of the pump housing, and then the anode can be held in place by securing at least one anode to a power supply point, possibly by welding.

[0027] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and in combinations other than those explicitly set out in the claims.

[0028] Where features of a device are described as operable to provide a certain function, this should be understood to include features of a device that provide that function or that are adapted or configured to provide that function.

[0029] Next, embodiments of the present invention will be further described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0030] [Figure 1] 1 illustrates a schematic internal configuration of an ion pump according to one embodiment. [Figure 2] 1 illustrates a schematic representation of a pump housing according to one embodiment. [Figure 3] FIG. 2 is a flow diagram illustrating steps of a method according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] Before describing the embodiments in more detail, an overview will first be provided.

[0032] This design is intended to simplify the mounting of the cathode plate in a typical miniature ion pump: the cathode plate slides along a path defined by support means, in some embodiments along rails, at the edges of the pump body, which in turn hold the cathode plate in place.

[0033] This is particularly effective for small ion pumps with pumping speeds of around 3 liters / second (as space for mounting the anode and cathode is limited, difficult to access, and difficult to manufacture). This configuration allows the cathode to be slid into the pump body, which is then held in place, making it easier to weld the closure / inlet flange over the opening, as the cathode should not move during the welding process.

[0034] The embodiment relates to a method for fixing a cathode to a pump body in a small (nominal 3 liters / second) ion pump.

[0035] FIG. 1 shows one embodiment of a Penning ion pump 10 with an anode assembly 1 including an array of tubes extending parallel to one another, positioned toward the center of a pump housing 12. Cathode plates 2 are attached to either side of the anode tubes, perpendicular to the anode tubes and spaced a predetermined distance from them. The cathodes 2 are typically made of titanium, but can also be made of other ultra-high vacuum safety conductors such as tantalum or aluminum. In some embodiments, the ion pump includes a Noble Diode variant in which the plates are made of different materials: one is made of titanium and the other is made of tantalum. In the illustration, the pump housing has openings 14 in its sidewalls through which the cathodes and anodes can be slid into place. When in place, a cover plate can be welded over the openings to form a vacuum-tight seal around the openings.

[0036] In this embodiment, the cathode plates are held on either side of the anode by support means in the form of rails 3 arranged to support the upper and lower edges of each plate. The cathode plate 2 is a flat plate which may or may not have support posts 4 extending therefrom. These support posts may be secured to the plate by welding. The anode 1 and cathode 2 are mounted such that the support post 4 extends through the centre of one or more anode tubes 1. The support posts provide additional electrons, particularly when starting the pump at low pressure.

[0037] As shown, the posts extending into the tube make assembly of the pump more difficult. By arranging the mounting means so that the cathode 2 can be slid into position along the path defined by the support means 3, the anode 1 and cathode 2 can be positioned outside the pump housing with the posts extending into the anode tube and the entire arrangement can be slid into position together.

[0038] In this embodiment, the rail 3 is a tube with a slit cut longitudinally along the rail the width of the cathode plate. The tube is made of the same material as the pump body to facilitate welding the rail to the pump body. The rail can be shaped differently from the tube. Alternatively, the support means can include multiple elements positioned on either side of the cathode plate to form a linear path along which the cathode plate can slide. These support means can include protrusions extending from one or both of the bottom and ceiling of the pump housing.

[0039] In another embodiment, shown in Figure 2, the attachment means may be formed into the pump body at the time of manufacture by means such as extrusion or machining. Figure 2 shows such an arrangement, where grooves 6, 7 in the bottom and ceiling of the pump housing 12 are provided on the inner surface of the pump housing to receive the cathode plate.

[0040] FIG. 3 shows a flow diagram illustrating steps of a method according to an embodiment.

[0041] In step S10, the anode array is positioned so that the support posts extending from the cathode plate extend into the anode tube. This is an optional step and will only occur if there are support posts extending from the cathode plate. Next, in step S20, the anode array and cathode plate are moved together into position within the pump housing, with the cathode plate sliding along a path defined by the support means. If the cathode plate does not have support posts, the anode and cathode can be positioned within the pump housing in separate steps.

[0042] In step S30, a second cathode plate is slid into position along a path defined by the support means on the opposite side of the anode array. These steps can be performed in a different order, and step S30 can be performed before steps S10 and S20.

[0043] Next, in step S40, the anode array is welded to a feed point that supplies voltage to the anode array to hold it in place.

[0044] In step S50, a closure plate is welded to cover the openings in the pump housing through which the anode and cathode are inserted, completing the pump assembly. The closure plate can be part of a side wall or wall of the pump housing, or can include the pump inlet. The weld should form a vacuum-tight seal around the openings.

[0045] In summary, an advantage of the embodiment is that the cathode plate(s) are held in place by a support means and do not need to be welded to the pump body, which can result in excessive heat and warping in small ion pumps. Furthermore, because the cathode is made of titanium and the pump body is made of stainless steel, welding one to the other can be difficult.

[0046] Although exemplary embodiments of the present invention have been disclosed in detail herein with reference to the accompanying drawings, it is understood that the present invention is not limited to the precise embodiments, and that various changes and modifications can be made by those skilled in the art without departing from the scope of the present invention as defined by the appended claims and their equivalents. [Explanation of symbols]

[0047] 1 Anode 2 cathode plates 3 Rail 4 pillars 6, 7 grooves 10 Ion Pump 12 Pump housing 14 Openings

Claims

1. a pump housing surrounding the pump chamber; at least one anode; at least one cathode comprising a plate; at least one mounting means configured to support said at least one cathode in a predetermined position within said pumping chamber; An ion pump comprising: the at least one mounting means comprises a support means defining a linear path, the linear path having an open end, the at least one cathode being slidable through the open end and along the linear path to the predetermined position.

2. 2. The ion pump of claim 1, wherein the ion pump comprises a pair of the mounting means for each of the at least one cathode plate, the pair of mounting means configured to support opposite ends of each of the at least one cathode plate, each of the pair of mounting means comprising support means defining the linear path having the open end.

3. 3. The ion pump of claim 1 or 2, wherein the at least one mounting means comprises a rail and the linear path comprises a groove extending along the length of the rail.

4. 3. The ion pump of claim 1 or 2, wherein the at least one mounting means comprises a plurality of support means arranged in an array, the array defining the linear path.

5. 3. The ion pump of claim 1 or 2, wherein the at least one attachment means comprises a groove on an inner surface of the pump housing.

6. 5. The ion pump of claim 1, wherein the at least one attachment means is welded to an inner surface of the pump housing.

7. 7. An ion pump according to claim 1, wherein the pump comprises two cathode plates attached to opposite ends of the at least one anode.

8. 8. The ion pump of claim 1, wherein the at least one anode comprises a cylinder and the at least one cathode is mounted perpendicular to a longitudinal axis of the cylinder.

9. 9. The ion pump of claim 8, wherein the ion pump comprises a plurality of cylindrical anodes mounted in an array, the axes of the cylindrical anodes being parallel to one another.

10. 10. The ion pump of claim 8 or 9, wherein at least one of the at least one cathode plate comprises at least one post extending from a surface of the at least one cathode plate toward the at least one anode and configured to protrude into the corresponding at least one cylindrical anode.

11. 11. The ion pump of claim 1, wherein the ion pump comprises a miniature ion pump having a nominal pumping speed of less than 4 liters per second.

12. A method for assembling the ion pump according to any one of claims 1 to 11, comprising the steps of: sliding the at least one cathode plate into an opening in a wall of the pump housing along the linear path defined by the support means; fixing the at least one anode to a power supply point on a wall of the pump housing facing the opening; A method for assembling an ion pump comprising:

13. 13. The method of assembling an ion pump of claim 12, further comprising the step of obscuring at least a portion of the opening by welding one of a closure plate or an inlet flange to the pump housing around the opening.

14. The method comprises: positioning the at least one cylindrical anode such that support posts extending from the at least one cathode plate extend into the at least one cylindrical anode; Including the initial step of Sliding the at least one cathode into position may include sliding the at least one anode and the at least one cathode into position together; A method for assembling the ion pump according to claim 12 or 13, comprising:

15. 15. The method of assembling an ion pump according to claim 12, wherein the step of fixing the at least one anode to the power supply point includes the step of welding the at least one anode to the power supply point.

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